1. Field of Invention
The invention relates to a combustor for a gas turbine engine.
2. Description of Related Art
In particular it concerns an improved means for cooling the air intake chutes of a gas turbine combustor, especially a means for configuring the surface of an air intake chute so as to enhance the heat transfer between the chute and the air flowing through it.
The majority of the air entering a combustor enters at the upstream (front) end, usually close to the fuel injection points. The air mixes with and aids the vaporization of the fuel, which then ignites and burns. Throughout this process the bulk motion of the combusting gas is from the front to the back of the combustor, exiting to the turbine.
This simple air and fuel mixing method does not achieve complete combustion and may result in undesirable unburned carbon and hydrocarbon emissions as well as a non optimal turbine entry temperature profile. A commonly used solution to this situation is to pierce the combustor wall by a plurality of plain holes to provide extra, or ‘dilution’, air to complete the combustion process. However, because the holes direct relatively small quantities of air into the combustor, usually perpendicular to the bulk flow, the momentum of the dilution air is much lower and therefore will have an insufficient penetration depth to be fully effective. An improvement can be obtained to employ air intake chutes in the holes to shield the dilution air from the main gas flow and help turn the air direction to a steep angle to the main flow.
The chutes suffer the drawback that because they are placed immediately downstream of the fuel injectors they experience overheating and subsequent erosion due to exposure to high temperatures and their close proximity to the combustion region. The present invention seeks to avoid this drawback.